I just did a fresh new installation of Snagit on macOS Catalina but now Snagit is in German. My O.S. is in Italian and I don't speak German at all. How can switch to English as it was until a week ago?
This will actually be configured in macOS System Preferences. Since Snagit doesn't have Italian translations, macOS picks the next language in the list that is supported which in your case is probably German. All you need to do is move English up to second in the list (and then restart Snagit) as shown here: